 Okay, for the second problem, we're doing another straight conversion from one set of units to a similar set of units, so density to density. We're going from grams per cubic centimeter to kilograms per meter cubed. So the two conversion factors that you need are up there at the top of the page. The one kilogram equals 1,000 grams and one meter equals 100 centimeters. Both of them you should know by now, you should know your metric to metric conversions. So the density in kilograms per meters cubed, how do you calculate it? Well, you just get the density of aluminum that the problem gave you, 2.7 grams per cubic centimeter. And then you take the grams and convert it to kilograms because that's the eventual mass unit you want. So use that first conversion factor, put in the grams at the bottom, kilograms at the top, those cancel. So now you're in units of kilograms per cubic centimeter. So remember that the conversion factor is one meter equals 100 centimeters. So we got to remember to cube the whole conversion factor, not just the centimeters and meters. So oftentimes we forget our undergraduate students forget to cube the 100, the number 100. So I like to show you that for the first time to just do it three times like that. So you can see it that you're actually using that conversion factor three times. So you're canceling out centimeters, centimeters, and centimeters again. And then if you multiply meters, dims, meters, dims, meters in the bottom, you get meters squared. So that will give you your units of kilograms per meter squared. So when you multiply all that out, you get 2.7 times 10 cubed or 10 to the third kilograms per meters cubed. So in order to do it the quicker way, so you don't have to write all those centimeters per meters conversion factors. You can just, like I said, cube the entire conversion factor 100 centimeters over one meter and then cube that whole thing. And as you see, you get the same answer. So remember your sig figs, two sig figs in the answer. If the given numbers had two sig figs, which they did 2.7. Okay, hopefully this helps. Let me know if you have any questions.